The appliance of science

Politicians and the public look to scientists to explain the causes of climate change and whether it can be tackled - and they are queuing up to deliver. But, asks Mike Hulme, are we being given the whole picture?

Climate change is happening, but it appears that science is split on what to do about it. One of the central reasons why there is disagreement about how to tackle climate change is because we have different conceptions of what science is, and with what authority it speaks - in other words, how scientific "knowledge" interacts with those other realms of understanding brought to us by politics, ethics and spirituality.

Two scientists - one a climate physicist, the other a biologist - have written a book arguing that the warming currently observed around the world is a function of a 1,500-year "unstoppable" cycle in solar energy. The central thesis is linked to evidence that most people would recognise as being generated by science. But is this book really about science?

It is written as a scientific text, with citations to peer-reviewed articles, deference to numbers, and adoption of technical terms. A precis of the argument put forward in the book by Fred Singer, an outspoken critic of the idea that humans are warming the planet, and Dennis Avery is that a well-established, 1,500-year cycle in the Earth's climate can explain most of the global warming observed in the last 100 years (0.7C), that this cycle is in some way linked to fluctuations in solar energy, and because there is nothing humans can do to affect the sun we should simply figure out how to live with this cycle. We are currently on the upswing, they say, warming out of the Little Ice Age, but in a few hundred years will be back on the downswing. Efforts to slow down the current warming by reducing emissions of greenhouse gases are at best irrelevant, or at worst damaging for our future development and welfare.

This, of course, is not what the fourth assessment report of the UN Intergovernmental Panel on Climate Change (IPCC) said a few weeks ago. The report from its climate science working group concluded that it is likely that most of the warming of the last 50 years has been caused by rising greenhouse gas concentrations and that, depending on our actions now to slow the growth of emissions, warming by 2100 will probably be between about 1.5C and 6C.

The upper end of this range is almost an order of magnitude larger than the warming that Singer and Avery suggest is caused by the 1,500-year cycle. So is this a fight between scientific truth and error? This seems to be how Singer and Avery would like to present it - "science is the process of developing theories and testing them against observations until they are proven true or false".

Means of inquiry

At one level, it is as simple as this. Science as a means of inquiry into how the world works has been so successful because it has developed a series of principles, methods and techniques for being able to make such judgments. For example, we now understand the major transmission routes for HIV/Aids, that smoking injures health, and that wearing seat belts saves lives.

And so it is with climate change. Increasing the concentration of greenhouse gases in the atmosphere warms the planet and sets in motion changes to the way the weather is delivered to us, wherever we are. Science has worked hard over a hundred years to establish this knowledge. And new books such as Singer and Avery's, or opinion pieces in the Daily Mail, do not alter it.

So far so good. Deploying the machinery of scientific method allows us to filter out hypotheses - such as those presented by Singer and Avery - as being plain wrong. But there are two other characteristics of science that are also important when it comes to deploying its knowledge for the benefit of public policy and society: that scientific knowledge is always provisional knowledge, and that it can be modified through its interaction with society.

That science is an unfolding process of discovery is fairly self-evident. The more we seem to know, the more questions we seem to need answering. Some avenues of scientific inquiry may close off, but many new ones open up. We know a lot more about climate change now than 17 years ago when the first IPCC scientific assessment was published. And no doubt in another 17 years our knowledge of how the climate system works and the impact that humans have made on it will be significantly different to today.

Yet it is important that on big questions such as climate change scientists make an assessment of what they know at key moments when policy or other collective decisions need to be made. Today is such a time.

But our portrayal of the risks of climate change will always be provisional, subject to change as our understanding advances. Having challenges to this unfolding process of discovery is essential for science to thrive, as long as those challenges play by the methodological rule book that science has painstakingly written over many generations of experience.

The other important characteristic of scientific knowledge - its openness to change as it rubs up against society - is rather harder to handle. Philosophers and practitioners of science have identified this particular mode of scientific activity as one that occurs where the stakes are high, uncertainties large and decisions urgent, and where values are embedded in the way science is done and spoken.

It has been labelled "post-normal" science. Climate change seems to fall in this category. Disputes in post-normal science focus as often on the process of science - who gets funded, who evaluates quality, who has the ear of policy - as on the facts of science.

So this book from Singer and Avery can be understood in a different way: as a challenge to the process of climate change science, or to the values they believe to be implicit in the science, rather than as a direct challenge to scientific knowledge.

In this reading, Singer and Avery are using apparently scientific arguments - about 1,500 year cycles, about the loss of species, about sea-level rise - to further their deeper (yet unexpressed) values and beliefs. Too often with climate change, genuine and necessary debates about these wider social values - do we have confidence in technology; do we believe in collective action over private enterprise; do we believe we carry obligations to people invisible to us in geography and time? - masquerade as disputes about scientific truth and error.

We need this perspective of post-normal science if we are going to make sense of books such as Singer and Avery's. Or indeed, if we are to make sense of polar opposites such as James Lovelock's recent contribution The Revenge of Gaia, in which he extends climate science to reach the conclusion that the collapse of civilisation is no more than a couple of generations away.

The danger of a "normal" reading of science is that it assumes science can first find truth, then speak truth to power, and that truth-based policy will then follow. Singer has this view of science, as do some of his more outspoken campaigning critics such as Mark Lynas. That is why their exchanges often reduce to ones about scientific truth rather than about values, perspectives and political preferences. If the battle of science is won, then the war of values will be won.

If only climate change were such a phenomenon and if only science held such an ascendancy over our personal, social and political life and decisions. In fact, in order to make progress about how we manage climate change we have to take science off centre stage.

This is not a comfortable thing to say - either to those scientists who still hold an uncritical view of their privileged enterprise and who relish the status society affords them, or to politicians whose instinct is so often to hide behind the experts when confronted by difficult and genuine policy alternatives.

Two years ago, Tony Blair announced the large, government-backed international climate change conference in Exeter by asking for the conference scientists to "identify what level of greenhouse gases in the atmosphere is self-evidently too much".

This is the wrong question to ask of science. Self-evidently dangerous climate change will not emerge from a normal scientific process of truth seeking, although science will gain some insights into the question if it recognises the socially contingent dimensions of a post-normal science. But to proffer such insights, scientists - and politicians - must trade (normal) truth for influence. If scientists want to remain listened to, to bear influence on policy, they must recognise the social limits of their truth seeking and reveal fully the values and beliefs they bring to their scientific activity.

Chink of weakness

Lack of such reflective transparency is the problem with "unstoppable global warming", and with some other scientific commentators on climate change. Such a perspective also opens a chink of weakness in the authority of the latest IPCC science findings.

What matters about climate change is not whether we can predict the future with some desired level of certainty and accuracy; it is whether we have sufficient foresight, supported by wisdom, to allow our perspective about the future, and our responsibility for it, to be altered. All of us alive today have a stake in the future, and so we should all play a role in generating sufficient, inclusive and imposing knowledge about the future. Climate change is too important to be left to scientists - least of all the normal ones.

· Mike Hulme, a professor in the school of environmental sciences at the University of East Anglia and the founding director of the Tyndall Centre for Climate Change Research, is writing a book, entitled Why We Disagree About Climate Change

· Unstoppable Global Warming - Every 1,500 Years, by S Fred Singer and Dennis T Avery, is published by Rowman & Littlefield (£21.72). The Guardian and Observer Climate Change Summit will take place in June 2007. For more details visit theguardian.com/climatesummit

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